The source sound is PCM but I'm sampling it with PWM (I use the uC for that ) , the original PCM raw file ( I generated from my PC using Audacity and xxd command ) is 8bit 8Khz signal but the uC generate it at twice bandwidth 16KHz to catch up (with the real wave shape ) , (the uC have timer that handle this ) when I set PWM frequency at 8KHz the sound were too noisy with a lot of cracks .The OP said the signal is PCM (audio samples), not PWM (Pulse Width Modulation). The audio system looks like a Bluetooth receiver that would produce ordinary audio
Unfortunately I don't have oscilloscope but the output signal should look similar to this (this is not the actual wave ) .
![Delta-PWM-svg.png](/forums/proxy.php?image=https%3A%2F%2Fi.ibb.co%2FP1Rfm4t%2FDelta-PWM-svg.png&hash=ec3e0cba5112dae42fe69442c22c6745)